Rubber compositions



United States Patent RUBBER cor oosirloNs John C. I-Iillyer,Bartlesville, Okla, assignor to Phillips Petroleum Company, acorporation of Delaware N0 Drawing. Application May 20, 1954, Serial No.431,293

15 Claims. (Cl. 2609304) This invention relates to novel compositions ofmatter. In one of its more specific aspects, it relates to rubberlike,vulcanizable compositions comprising a rubber and a polycyclic alcohol.In another of its more specific aspects, it relates to polycyclicalcohols as softeners, and/ or tackifiers for synthetic and/or naturalrubber. In still another of its more specific aspects, it relates toelastomer compounding.

This application is a continuation-impart of my copending U. S.application Serial No. 255,520, filed November 8, 1951.

I have now discovered that polycyclic alcohols are good softeners and/ortackifiers for synthetic and/or natural rubber. The polycyclic alcoholsused in this invention can be represented by the general formula .H I si as. R,,.C G -R Real -R Hr on Wherein each R is of the group consistingof hydrogen and methyl and at least one R is hydrogen, and each R is ofthe group consisting of hydrogen and an alkyl group having not more than3 carbon atoms with the sum of the carbon atoms in the Rm and in the Rnin each case, not greater than three and at least two of the Rm and ofthe R'n are hydrogen. These novel alcohols are soluble in most of thecommon solvents such as benzene, isopentane, n-pentane, n-heptane,methanol, ethanol and others.

The following are objects of the invention.

It is an object of this invention to provide softeners and/ ortackifiers for natural and/ or synthetic rubbers.

Another object of this invention is to provide a process for compoundingrubber-like vulcaniz-able organic elastomers.

A further object of this invention is to provide a rubber-'- like,vulcanizable composition of matter.

Further objects and advantages of this invention will become apparent toone skilled in the art from the accompanying disclosure and discussion.The polycyclic alcohols can be prepared by the reduc tion of thecorresponding aldehydes by suitable means, such as by a crossedCannizzaro reaction. "Polycyclic aldehydes from which the materials canbe prepared are fully described in the patent application of J. C.Hill'yer et al., Serial No. 81,413, filed March '14, 1949' and nowPatent No. 2,683,151, the disclosure of which is incorporated into andmade a part of this disclosure. This patent application also describes amethod for the production of said aldehydes.

The polycyclic aldehydes from which the polycyclic alcohols are preparedare obtained by reacjing a suitable the corresponding diolefins with amethyl furfural.

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. 2 diolefin with a suitable furfural. As the diolefin reactant it ispreferred to use a conjugated diolefin, preferably a conjugated diolefinhaving not more than about 7 carbon atoms per molecule. Such a diolefincan be referred to as a memberof the group consisting of 1,3-butadieneand its immediate homologues and may be reported as having the formulaH- wherein each R is of the group consisting of hydrogen and an alkylgroup having not more than three carbon atoms and wherein at least two Rare hydrogen atoms. The furfural reactant employed in the practice ofthis invention can be referred to as one of the group consisting offurfural and its immediate homologues having not more than six carbonatoms per molecule, such as an alkyl substituted furfural having notmore than six carbon atoms per molecule. Such material may berepresented by the general formula wherein each R is of the groupconsisting of hydrogen and a methyl group and wherein at least one R isa hydrogen atom.' The more commonly used reactants employed as startingmaterials in the production of the polycyclic aldehydes prior to thepreparation of the polycyclic alcohols therefrom include '1,3-butad ieneand furfural, isoprene and furfural, piperylene and furfural and Itappears that in producing the raw material polycyclic aldehyde, twomolecules "of the diolefin react with one molecule of the furfuralreactant by a. modification of the Diels-Alcler reaction.

Typical polycyclic alcohols which can be used in the practice of thisinvention are 2,3,4,5-bis-(A -butenylene)- tetrahydrofurfuryl alcohol,3methyl-2,3,4,5-bis(.A -butenylene)-tetrahydrofurfuryl alcohol,4-methyl-2,3,4,5-bis- (3-methyl-A -butenylene)-tetrahydrofurfurylalcohol, 3,5- dimethyl-2,3,4, 5-bis(2,3,dimethyl A butenylene)-t etrahydrofurfuryl alcohol, 2,3 (2-isopropyl A? butenylene 4,5(4-methyl-A-butenylene) tetrahydrofurfuryl alcohol, and S-methyl-Zfi (Zr-methyl Abutenylene) -4,5-(2-ethyl- A -butenylene)-tetrahydrofurfuryl alcohol aswell as their higher and lower molecular weight homologues. Aparticularly preferred polycyclic alcohol is 2,3,4, 5-b is( Abutenylene)-tetrahydrofurfuryl alcohol.

In its broadest aspect, my invention applies to providing polycyclicalcohols as softeners or tackifiers for vulc an izable organicelastomers containing unsaturated carbon to carbon bonds. My inventionapplies to softening or tackifying natural rubber or rubber-likepolymers produced the polymerization of aliphatic conjugated dienes,particularly those having from .4 to 6 carbon atoms per molecule, suchas butadiene, isoprene, pentadienes, etc or the copolymerization of suchdienes with a compound containing a CHz=C group copolymerizabletherewith, such as styrene, acrylonitrile, etc. The polycyclic alcoholscan be used in the processing of sulfur vulcanizable organic elastomers.The polycyclic alcohols used in the practice of my invention are veryadvantageously applied to the compounding of the relatively newlow-temperature synthetic rubbers which are prepared by copolymerizingbutadiene with styrene, with methylvinylpyridine, with acrylonitrile,and with other monomers in an emulsion system at a temperature of from20 to 1 5 C. The softeners and/ or tackifiers of my invention can beused with butyl rubber stocks which are produced by copolymerizing amajor quantity of isobutylene. with 3 a minor quantity of a conjugateddiene, such as those mentioned hereinbefore. The softeners and/ ortackifiers of my invention can be used with reclaimed natural orsynthetic rubbers and with various mixtures of natural, synthetic,reclaimed natural and reclaimed synthetic rubber.

The amount of polycyclic alcohols employed as softeners or tackifierswill vary depending upon the type of polymer being processed and theproperties desired in the finished product. It will usually be in therange of l to 75, preferably in the range of 1 to 50, parts by weightper 100 parts by weight of rubber and more desirably in the range of 3to parts by weight per 100 parts by weight of rubber, the larger amountsbeing used for high Mooney viscosity materials.

Vulcanizable organic elastomer compositions usually contain otheringredients including fillers; modifiers; softeners, tackifiers, andplasticizing substances; Vulcanizing agents; age resistors orantioxidants; and accelerators of vulcanization; accelerator activators;etc. The exact composition of the vulcanizable organic elastomercomposition depends upon the use to which the vulcanizable compositionis to be put. The new softeners and tackifiers of my invent-ion can beused in any of the various compounding rec1pes.

Carbon black is added to many vulcanizable organic elastomer mixesduring compounding as a filler. In some instances the carbon black orother filler is added to the latex of the polymer prior to coagulation.Other ingredients such as the softener may also be added in this manner.This technique is usually termed m'asterbatching. There are many typesof carbon blacks used today in compounding, among which are: recentlydeveloped high pH furnace carbon blacks having a pH of from 8.0 to 10.5,usually 8.6 to 10.1, such as high abrasion furnace carbon blacks (HAFblacks), superabrasion furnace blacks (SAF blacks) and high modulusfurnace carbon blacks (HMF blacks); reinforcing furnace blacks (RFblacks) and very fine furnace blacks (VFF blacks); easy, medium, or hardprocessing channel blacks; lamp blacks; fine and medium thermal carbonblacks; acetylene carbon blacks; semireinforcing furnace carbon blacks;conductive furnace and conductive channel carbon blacks; and highelongation furnace carbon blacks. Other pigments or additives, such asferric oxide, magnesium carbonate, titanium dioxide, zinc oxide,hydrated alumina, kieselguhr, slate dust, zinc peroxide, zinc chloride,lead peroxide, lead oxide, chlorinated paraflins, glue, barytes, fossilflour, lithopone, various clays, finely divided silica, whiting, etc.,can be added as fillers or to modify the properties of the vulcanizablecomposition or vulcanized composition, such properties as the rate ofcure, resistance to scorching during processing, activation ofacceleration, etc.

The polycyclic alcohols employed as softeners and tackifiers can be usedalone or as mixtures with each other or in conjunction with othersofteners and tackifiers. There are many such latter substances, amongwhich are vegetable oils, such as palm oil, rape oil, olive oil, linseedoil, oastor bean oil, soya bean oil, tung oil; bitumens includingso-called mineral rubbers, which comprise natural products, such asgilsonite, raphaelite, and also high-boiling petroleum residues,asphalts, etc.; pine tar; paraflin wax; mineral oils; fatty acids, suchas oleic acid, stearic acid, palmitic acid, lauric acid, etc.; ceresin;naphthalenes; rosin; wool grease; carnauba wax; the many organicchemical compounds, such as glycerol, glyceryl monostearate, glycerylmonooleate, glyceryl monoricinoleate, trioctyl phosphate, triglycoldioctoate, ethylene glycol monostearate and the monooleate,phenol-formaldehyde thermosetting resins, poly-alpha-methyl styrene, andother polymers of styrene and substituted styrene, dioctyl phthalate,dioctyl sebacate, polybutenes, zinc resinate, coumarone resins,dihydroabietic acid, etc. Most of these compounds aid tackiness as wellas soften the vulcanizable organic elastomers. Also, some of themexhibit modifying characteristics.

Vulcanizing agents are added to vulcanize the organic elastomers duringthe vulcanization step of processing. There are a wide variety ofVulcanizing agents, such as: sulfur, including powdered sulfur, or inone or more other forms, and mixtures thereof; so-called plasticsulfurs; sulfur-containing compounds, such as sulfur chloride, hydrogensulfide, sulfur thiocyanate, tetraalkylthiuram disulfides, etc.;selenium; tellurium; benzoyl peroxide; trinitrobenzene; dinitrobenzene;nitrobenzene; quinones; certain inorganic oxidizing agents;diazoaminobenzene and its derivatives; other nitrogen-containingcompounds, etc.

Accelerators of vulcanization are added to accelerate vulcanizationduring the vulcanization step of processing. There are many well knownaccelerators of vulcanization, such as: thioureas; thiophenols;mercaptans; dithiocarbamates; xanthates; trithiooarbonates; dithioacids, mercaptothiazoles; mercaptobenzothiazoles; thiuram sulfides;organic-cobalt chelates; etc., and various mixtures thereof. Some widelyused and particularly good accelerators are, for instance,mercaptobenzothiazole, benzothiazyl disulfide, diphenylguanidine, zincsalt of mercaptobenzothiazole, zinc benzothiazyl sulfide,tetramethylthiuram disulfide, N-cyclohexyl-2-benzothiazole sulfenamide,aldehydeammonias, triphenylguanidine, zinc dibutyl and zinc dimet'nyldith-iocarbanrate, many others, and mixtures thereof. Acceleratoractivators are also employed to advantage in some instances.

In most cases it is the usual practice to add age resistors orantioxidants to vulcanizable organic elastomer mixes during the mixingstep of processing in order to slow down or prevent the deterioration ofthe vulcanized product. Antioxidants or age resistors have the propertyof maintaining tensile strength, resistance to abrasion, elasticity,preventing flex cracking, etc. One or more antioxidants are usuallyemployed, such as phenyl-beta-naphthylamine, p-aminophenol,hydroquinone, p-hydroxydiphenyl, diphenylamine, 2,4-toluenediamine,p-ditolylamine, o-ditolyamine, beta-naphthyl-nitrosoamine, N,N'-diphenyldiaminoethane, phenyl-alpha-naphthylamine, p,p-diaminodiphenylmethane,etc.

The vulcanizable organic elastomer compositions resulting from admixingthe various ingredients with the new softeners and tackifiers of myinvention by the methods known in the prior art, are vulcanized in theusual manner after they are molded or shaped into the desired shape bythe numerous shaping operations of the prior art, such as calendering,casting from solution, continuous or discontinuous extrusion, molding inopen or closed molds, etc., and they can be used for the many purposesfor which other similar compositions are used. For example, they can beused for tire tubes, tire treads, tire casings, shoe soles and heels,raincoats, table covers, hose for the transmission of fluids, belts,balloon coverings, printers rolls, printers blankets, engraving plates,aprons, gloves, masks, tanks, battery cases, friction tape, mats, wireinsulation, etc. Fabrics can be coated or impregnated by calendering orimpregnation with a suitable emulsion.

The softeners and tackifiers of my invention can be added to the rubberin any one of various ways. For example, they can be added during themilling operation along with one or more of the other compoundingingredients. In certain instances it is preferred to add the polycyclicalcohols to the latex of the polymer by the masterbatching technique. Bythis procedure the softener and tackifier, or mixture thereof, isemulsified in water and this emulsion is added to the latex prior tocoagulation. The softener and tackifier can, in some cases, be added tothe latex as a solution in a suitable hydrocarbon or other solvent, or,if desired, it can be added per se, i. e., without any solvent orsuspending agent.

A more comprehensive understanding of the invention may be obtained byreference to the following examples which are not intended, however, tobe unduly limitative of the invention.

5 EXAMPLE 1 Preparation of 2,3,4,5-bis(A -butenylefie)-tetrmydfo forthin Table No. 1.

Table No. 1

PHR i 300% Tensile Percent Shore Percent Mooney 9 Softener SoftenerModulus, p. s. i. Elonga- Hardness Compres- Value p. s. i. tion sion Set2,3,4,5-b'1s(N-butenylene) tetra- 1O 2, 090 2, 850 400 64 12. 2 44. 5hydrofuriuryl alcohol 2O 1, 850 2, 750 420 59 14. 1 34. 5

OVEN AGED 24 nouns AT 212 F.

2,3,4,5-bis(A*-buteny1ene)-tetra- 10 3, 250 3, 250 300 o1 20 290hydrofurfuryl alcoh PER-parts per 100 parts of rubber.

Oompounded Mooney value-small rotor for 1% minutes at 212 3. accordingto ASTM D92749T.

furfuryl alcohol. v

A run was made wherein 250 grams of potassium hydroxide was dissolved in375 ml. of methyl alcohol and the solution so formed added with stirringover a period of 30 minutes to 306 grams of 2,3,4,5bis(A -butenylene)-tetrahydrofurfural, said 2,3,4,5-bis(n butenylene) tetrahydrofurfuralbeing dissolved in 150 ml. of 40 Weight per cent aqueous formaldehydeand 400 ml. of methyl alcohol. Temperature of the reaction mixtureduring said addition was maintained at about 60 C. for 3 hours after theaddition was completed. Methanol was removed by vacuum distillation and450 ml. of water was then added. Phase separation occurred, the bottomlayer being the aqueous layer. The top layer, containing most of theproduct, was removed. The bottom layer was extracted with three 200 ml.portions of benzene. The benzene extract and the top layer were combinedand washed with five 50 ml. portions of water. Benzene was removed byvacuum distillation to provide 275.1 grams of crude 2,3,4,5 bis(Abutenylene) tetrahydrofurfuryl alcohol. The crude alcohol was a lightyellow, viscous liquid which slowly crystallized on standing at roomtemperature (25 C.).

The crude product was distilled under vacuum to provide pure2,3,4,5-bis(A -butenylene)-tetrahydrofurfuryl alcohol which was a whitecrystalline solid having a melting point of 33 to 35 C., refractiveindex n 1.5335, and a hydroxyl-number of 259. The pure product wasreadily soluble in benzene, isopentane, n-pentane, nheptane, methanol,and ethanol. The 2,4-dinitrobenzoate derivative of said 2,3,4,5-bis(A-butenylene)-tetrahydro furfuryl alcohol had a melting point of 75-77"C.

EXAMPLE II Parts by weight I II 1,3-butadiene-acrylonitrile copolymer100 100 Philblack A 1 60 60 Zinc oxide 5 5 Altax 2 1. 5 1. 5 StearicAcid 1. 5 2. Sulfur 1. 1. 75 Softener 1 Medium abrasion furnace black. 2Benzothiazyl disulfide.

The samples were compounded by mill mixing and cured HzC OH wherein R isselected from the group consisting of hydrogen and methyl radicalwherein at least one R is hydrogen, wherein each R is selected from thegroup consisting of hydrogen and an alkyl radical having not more than 3carbon atoms and wherein the sum of the carbon atoms in the R'm and inthe R'n in each case is not greater than 3 and wherein at least two ofthe Rm and at least two of the R'n are hydrogen.

2. The composition of claim 1 wherein said sulfur vulcanizable organicelastomer is a copolymer prepared by copolymerization of 1,3 butadieneand acrylonitrile in an emulsion system and said polycyclic alcohol ispresent in an amount in the range of 1 to 75 parts by weight per partsby weight of said vulcanizable organic elastomer.

3. The composition of claim 1 wherein said sulfur vuloanizable organicel-astomer is a copolymer prepared by copolymerization of bu-tadiene andstyrene in an emulsion system and said polycyclic alcohol is present inan amount in the range of l to 75 parts by weight per 100 parts byweight of said vulcanizable organic elas-tomer.

4. The composition of claim 1 wherein said sulfur vulcanizable elastomeris natural rubber and said polycyclic alcohol is present in an amount inthe range of 1 to 75 parts by weight per 100 parts by weight of saidnatural rubber.

5. The composition of claim 1 wherein said polycyclic alcohol is2,3,4,5-bis(n -butenylene) tetrahydrofurfuryl alcohol.

6. The composition of claim 1 wherein said polycyclic alcohol is3-methyl-2,3,4,5-'bis(A -butenylene)-tetrahydrofurfuryl alcohol.

7. The composition of claim 1 wherein said polycyclic alcohol is4-methyl-2,3,4,5-bis(3-methyl-A -bu-tenylene)- tetrahydrofurfurylalcohol.

8. A product of vulcanization comprising a sulfur vulcanizable organicelastomer which has been vulcanized with a vulcanizing agent in thepresence of a polycyclic alcohol represented by the general formula:

wherein R is selected from the group consisting of hydro 1 gen andmethyl radical wherein at least one R is hydrogen wherein each R isselected from the group consisting of hydrogen and an alkyl radicalhaving not more than 3 carbon atoms and wherein the sum of the carbonatoms in the Rm and in the R'n in each case is not greater than 3 andwherein at least two of the Rm and at least two of the R'n are hydrogen.

9. A vulcanizate of claim 8 wherein said sulfur vulcanizable organicelastomer is a copolymer prepared by copolymerization of 1,3-butadieneand acrylonitrile in an emulsion system and said polycyclic alcohol ispresent in an amount in the range of 1 to 75 parts by weight per 100parts by weight of said vulcanizable organic elastomer.

10. A vulcanizate of claim 8 wherein said sulfur vulcanizable organicelastomer is a copolymer prepared by copolymerization of butadiene andstyrene in an emulsion system and said polycyclic alcohol is present inan amount in the range of 1 'to 75 parts by weight per 100 parts byweight of said vulcanizable organic elastomer.

11. A vulcanizate of claim 8 wherein said sulfur vulcanizable elastomeris natural rubber and said polycyclic alcohol is present in an amount inthe range of l to 75 parts by weight per 100 parts by weight of saidnatural rubber.

12. The vulcanizate of claim 8 wherein said polycyclic alcohol is2,3,4,5-bis(A -butenylene)-tetrahydrofurfuryl alcohol.

13. The vulcanizate of claim 8 wherein said polycyclic alcohol is3-methyl-2,3,4,5-bis(A -butenylene)-tetrahydrofurfuryl alcohol.

14. The vulcanizate of claim 8 wherein said polycyclic alcohol is4-1nethyl-2 ,3,4,5-bis(3-methyl-A -butenylene)- tetrahydrofurfurylalcohol.

15. The composition of claim 1 wherein said sulfur vulcanizable organicelastomer is a copolymer prepared by copolymerization of 1,3-butadieneand acrylonitrile and said polycyclic alcohol is 2,3,4,5-bis(A-butenylene)- tetrahydrofurfuryl alcohol, said alcohol being present inan amount in the range of 3 to 25 parts by weight per 100 parts byweight of said vulcanizable organic elastomer.

No references cited.

1. A RUBBER-LIKE, VULCANIZABLE COMPOSITION COMPRISING A RUBBER-LIKESULFUR VULCANIZABLE ELASTOMER AND A POLYCYCLIC ALCOHOL REPRESENTED BYTHE GENERAL FORMULA: